+# Copyright (c) 2006-2021. The SimGrid Team. All rights reserved.
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of the license (GNU LGPL) which comes with this package.
+
+# This example shows how to simulate a non-linear resource sharing for disk
+# operations.
+#
+# It is inspired on the paper
+# "Adding Storage Simulation Capacities to the SimGridToolkit: Concepts, Models, and API"
+# Available at : https://hal.inria.fr/hal-01197128/document
+#
+# It shows how to simulate concurrent operations degrading overall performance of IO
+# operations (specifically the effects presented in Fig. 8 of the paper).
+
+
+from simgrid import Actor, Engine, NetZone, Host, Disk, this_actor
+import sys
+import functools
+
+
+def estimate_bw(disk: Disk, n_flows: int, read: bool):
+ """ Calculates the bandwidth for disk doing async operations """
+ size = 100000
+ cur_time = Engine.get_clock()
+ activities = [disk.read_async(size) if read else disk.write_async(
+ size) for _ in range(n_flows)]
+
+ for act in activities:
+ act.wait()
+
+ elapsed_time = Engine.get_clock() - cur_time
+ estimated_bw = float(size * n_flows) / elapsed_time
+ this_actor.info("Disk: %s, concurrent %s: %d, estimated bandwidth: %f" % (
+ disk.name, "read" if read else "write", n_flows, estimated_bw))
+
+
+def host():
+ # Estimating bw for each disk and considering concurrent flows
+ for n in range(1, 15, 2):
+ for disk in Host.current().get_disks():
+ estimate_bw(disk, n, True)
+ estimate_bw(disk, n, False)
+
+
+def ssd_dynamic_sharing(disk: Disk, op: str, capacity: float, n: int) -> float:
+ """
+ Non-linear resource callback for SSD disks
+
+ In this case, we have measurements for some resource sharing and directly use them to return the
+ correct value
+ :param disk: Disk on which the operation is happening (defined by the user through the std::bind)
+ :param op: read or write operation (defined by the user through the std::bind)
+ :param capacity: Resource current capacity in SimGrid
+ :param n: Number of activities sharing this resource
+ """
+ # measurements for SSD disks
+ speed = {
+ "write": {1: 131.},
+ "read": {1: 152., 2: 161., 3: 184., 4: 197., 5: 207., 6: 215., 7: 220., 8: 224., 9: 227., 10: 231., 11: 233., 12: 235., 13: 237., 14: 238., 15: 239.}
+ }
+
+ # no special bandwidth for this disk sharing N flows, just returns maximal capacity
+ if (n in speed[op]):
+ capacity = speed[op][n]
+
+ return capacity
+
+
+def sata_dynamic_sharing(disk: Disk, capacity: float, n: int) -> float:
+ """
+ Non-linear resource callback for SATA disks
+
+ In this case, the degradation for read operations is linear and we have a formula that represents it.
+
+ :param disk: Disk on which the operation is happening (defined by the user through the std::bind)
+ :param capacity: Resource current capacity in SimGrid
+ :param n: Number of activities sharing this resource
+ :return: New disk capacity
+ """
+ return 68.3 - 1.7 * n
+
+
+def create_ssd_disk(host: Host, disk_name: str):
+ """ Creates an SSD disk, setting the appropriate callback for non-linear resource sharing """
+ disk = host.create_disk(disk_name, "240MBps", "170MBps")
+ disk.set_sharing_policy(Disk.Operation.READ, Disk.SharingPolicy.NONLINEAR,
+ functools.partial(ssd_dynamic_sharing, disk, "read"))
+ disk.set_sharing_policy(Disk.Operation.WRITE, Disk.SharingPolicy.NONLINEAR,
+ functools.partial(ssd_dynamic_sharing, disk, "write"))
+ disk.set_sharing_policy(Disk.Operation.READWRITE,
+ Disk.SharingPolicy.LINEAR)
+
+
+def create_sata_disk(host: Host, disk_name: str):
+ """ Same for a SATA disk, only read operation follows a non-linear resource sharing """
+ disk = host.create_disk(disk_name, "68MBps", "50MBps")
+ disk.set_sharing_policy(Disk.Operation.READ, Disk.SharingPolicy.NONLINEAR,
+ functools.partial(sata_dynamic_sharing, disk))
+ # this is the default behavior, expliciting only to make it clearer
+ disk.set_sharing_policy(Disk.Operation.WRITE, Disk.SharingPolicy.LINEAR)
+ disk.set_sharing_policy(Disk.Operation.READWRITE,
+ Disk.SharingPolicy.LINEAR)
+
+
+if __name__ == '__main__':
+ e = Engine(sys.argv)
+ # simple platform containing 1 host and 2 disk
+ zone = NetZone.create_full_zone("bob_zone")
+ bob = zone.create_host("bob", 1e6)
+ create_ssd_disk(bob, "Edel (SSD)")
+ create_sata_disk(bob, "Griffon (SATA II)")
+ zone.seal()
+
+ Actor.create("", bob, host)
+
+ e.run()
+ this_actor.info("Simulated time: %g" % Engine.get_clock())
+
+ # explicitly deleting Engine object to avoid segfault during cleanup phase.
+ # During Engine destruction, the cleanup of std::function linked to non_linear callback is called.
+ # If we let the cleanup by itself, it fails trying on its destruction because the python main program
+ # has already freed its variables
+ del(e)